Structure visible in the corona. (ISO 200, 1/1000 s exposure.)
Mercury visible below and to the left of the Sun. (ISO 200, 1/4 s exposure.)
The diamond ring effect at 3rd contact. (ISO 400, 1/1600 s exposure.)
Orwell Astronomical Society (Ipswich)
Solar Total Eclipse, 21 August 2017
The solar total eclipse of 21 August 2017 was the third of an annual run of the phenomenon before a gap in 2018. For 2017, the organised tour transported us from San Francisco to Jackson Hole, Wyoming via Las Vegas, Salt Lake City and Idaho Falls. The journey took in five national parks (Yosemite, Zion, Bryce, Yellowstone and Grand Teton) and seven states (California, Arizona (just), Nevada, Utah, Idaho, Montana and Wyoming). The parks were great, each one better than the last. The colours of geological rock formations in the parks were amazing. A high point was viewing Old Faithful geyser in Yellowstone. And we saw many bison and chipmunks.
The usual worry about the weather on eclipse day was overshadowed by the possibility that Guam, closely followed by San Francisco, would soon cease to exist due to nuclear conflict between North Korea and the USA. However, with a few days to go, worries about possible war evaporated as the TV news stations suddenly switched from a focus on the impending apocalypse to the "Great American Eclipse", broadcast on all channels, 24 hours a day. They rightly called the eclipse American as the only landfall made by the track was on the continental USA. Indeed, the hype before the event was as high as would be expected, including TV and press coverage; many and various T-shirts, hats and other clothing; eclipse guide books for every town and state; and, of course, personalised eclipse viewers for every store, gas station and facility.
We arrived at Jackson Hole the day before the eclipse in plenty of time to hear John Mason’s talk. This was up to his usual standard, if not better – providing details of the local circumstances and background for the "eclipse virgins" among our party.
So the day dawned. Our observing site was at Snake River Ranch, Jackson Hole, coordinates 43° 32’ 44"N, 110° 49’ 58"W. The site was a working cattle ranch that hires a field for conventions and weddings, etc. The eclipse ran from 1st to 4th contact from approximately 10.00am to 1.00pm. The weather forecast was for 50% cloud cover at dawn, clearing by lunchtime. In fact, the weather turned out to be better than forecast with much less cloud, and what there was disappeared very quickly. So we were all set.
By way of equipment, I had my usual computer-controlled camera, automatically timed to take appropriate exposures around and between 2nd and 3rd contacts. I also had a thermometer probe, linked via Bluetooth to an android tablet, measuring the temperature in the shade. Results are below. I placed a white sheet on the ground to act as a screen to display shadow bands. I tried to video the phenomenon from a minute before 2nd contact to a minute after 3rd. Unfortunately, the video did not properly record the remarkable bands that were visible to the naked eye. Others recorded better videos of the phenomenon on the backs of the white chairs provided! The bands themselves were easily visible to the naked eye just before 2nd contact and persisted for a long time after 3rd contact.
The eclipse itself was superb! Bailey’s beads led into and out of totality, forming a perfect diamond ring. During totality, it became dark and three large flares on the Sun’s limb were visible even with small binoculars, and possibly to the naked eye. Several planets were visible. I saw only Mercury and Venus, and didn't hear of anyone seeing more, although Jupiter (very low down) and Mars were also, in principle, visible. The mountains behind us formed an excellent backdrop on which to view first the approaching and then the receding lunar shadow. Even though my video of the shadow bands was not good, it did pick up the change in the lighting of the mountain background and, on the audio track, the reactions of spectators of the eclipse. My imaging suffered two minor problems. First, focus was not as sharp as it could have been and, second, the clock on my PC was a few seconds out, which meant that my photographs missed the Bailey’s beads at 2nd contact. My best images are below (all taken with a 300 mm lens, f5.6).
During totality, we heard cattle lowing, and John Mason claimed to hear a wolf howling. We had joked about this earlier but he insisted on his claim. I'm going over my audio recordings to see if I can provide corroborating evidence! We were also treated to an eagle flying overhead; in fact, there were many eagles in flight, along with vultures and geese before and after the eclipse. One couple celebrated their 41st wedding anniversary under the eclipse, while another became engaged – exchanging one diamond ring under another!
A full account of the eclipse and our group observing it may be found in the Independent Newspaper online. I was standing just to the left of the observer in the main photograph – so near yet so far! Roll on the two South America eclipses in 2019 and 2020.
The above graph shows the evolution of ambient temperature in the shade. C1, C2, C3 and C4 mark respectively the instants of 1st, 2nd, 3rd and 4th contacts. The warming effect of the Sun is countered by the increasing depth of eclipse between 1st contact and 11:15. Thereafter, there is a marked dip in temperature of some 6°C with a hysteresis delay evident after the end of totality (3rd contact) as the eclipse came to an end and the Sun's warmth took effect once more.
Structure visible in the corona. (ISO 200, 1/1000 s exposure.)
Mercury visible below and to the left of the Sun. (ISO 200, 1/4 s exposure.)
The diamond ring effect at 3rd contact. (ISO 400, 1/1600 s exposure.)
We saw a fantastic eclipse from Wind River, Wyoming (200 km east of where Paul Whiting observed). We saw excellent diamond rings at both 2nd and 3rd contact. I thought that the corona was unusually bright: this may have been due to the clarity of the atmosphere.
As usual, I dedicated the short duration of totality to visual observing. Whilst watching the eclipse I set a video running to capture the ambience of the eclipse and perhaps record some wildlife behaviour. I did catch a lot of whoops, wows and cheers from eclipse chasers - and even some applause after 3rd contact – but nothing from any other creature. I had expected to hear a reaction from orthoptera, the order of insects which includes grasshoppers, crickets and locusts, which I thought might start "singing" when the light level dropped. I knew that orthoptera were present because one landed on me while I was taking a pre-1st contact nap!
Our trip to observe the eclipse also took in the Thermopolis State Park, Lake Powell and the National Parks of Yellowstone, Grand Teton, Bryce Canyon and The Grand Canyon. Having seen Old Faithful geyser, I was inspired to sample Old Faithful Ale! The night sky from the National Parks is superb. In the Grand Canyon National Park from the parking lot of the lodge were we stayed at the South Rim, the Milky Way was brilliantly clear down to the horizon. We enjoyed great views of Messier objects with small binoculars (8x32 and 8x36).
Around a year before the eclipse of August 2017, I made the decision to observe it. Visiting the USA to see the eclipse seemed relatively easy (certainly compared to earlier target sites like Indonesia and Easter Island!) The primary task was, of course, to confirm my viewing site. With an American wife and a wide selection of family locations this looked straightforward; alas at the time none of my relatives lived near to the line of totality. By great good fortune, however, early in 2017 a relative moved to the small town of Payette Idaho at the junction of the Payette and Snake Rivers. Although situated a little way south of the centre line, the location provided my observing location for the eclipse.
I made preparations. Initially, I considered transporting telescopes and mounts to the USA for imaging. However, by good-luck my US sister-in-law sent me the Sky and Telescope "Guide to the Eclipse". This offered the advice that, especially for a first eclipse, the best approach might be to simply watch with the naked eye rather than waste time fiddling with an imaging system! I took the advice to heart and limited myself to my Canon 100D camera with a Tamron 18-400 lens. Pre-setting and pre-aligning the camera (on a fixed tripod) would allow me to watch the eclipse whilst taking a sequence of shots by remote shutter operation.
Fast forward to 21 August and my wife and I stood in the small back garden of our family host. Looking SE, we saw a dark cluster of trees. At 10.00am local time (Mountain Time), the sun crept around the trees. In due course the family gathered and, solar glasses in place, some four generations waited for the eclipse. At 10.10am the silhouette of the Moon began to bite into the visible solar disc. Time dragged as we waited the 1 hour 15 mins to totality. As totality neared, the environmental impact of the eclipse became clear: the silence grew (among both members of the family and birds!) and the world turned increasingly monochrome.
At 11.25am the glory of the total solar eclipse began. The experience is difficult to put into words: I can only repeat the oft stated view that everyone should see an eclipse – the beauty of the phenomenon is beyond mere words.
I took a number of images with varying settings during totality, drawing out corona, prominences and, of course, the "diamond ring". Totality was over in a "flash", both literally and metaphorically and the solar disc returned steadily for the next couple of hours. What a great event and a great family experience!
The first (compound) image below was taken by smartphone. Subsequent images were taken with my Canon 100D camera with a Tamron 18-400 lens (fixed at 400 mm).
The world turns monochrome towards totality! Images 1 hour and 5 mins before totality.
Corona. (1/40 s, f/6.3.)
Prominences. (1/1000 s, f/6.3.)
The diamond ring effect. (1/200 s, f/14.)
Montage of images throughout the eclipse.
See Fred Espenak's eclipse web site eclipse.gsfc.nasa.gov/eclipse.html.